Valarr was the son of Baelor "Breakspear" Targaryen, the crown prince of the Seven Kingdoms. Raised as a future king, Valarr was trained as a knight alongside his brother Matarys Targaryen. Valarr was known to look very similar to his father.
Valarr took part in the Ashford Tourney, and his status allowed him to sit as one of the five champions of Lady Ashford. Although any participating knight could challenge Valarr and take his place as a champion, his status as a Targaryen prince and grandson of the king prevented him from facing a legitimate opponent. In the first tilt he defeated Ser Abelar Hightower. Ser Duncan the Tall considered challenging Valarr before he was arrested for assaulting Valarr's cousin, Prince Aerion Targaryen. During the Trial of Seven, he lent his armor to his father because Baelor had not brought armor to the Tourney. During the joust, Valarr's father was killed, and Valarr became the heir apparent behind King Daeron II Targaryen. The young prince blamed Ser Duncan for his father's death, and in the future, Duncan would find Valarr in his dreams, blaming him fully for his father's death.